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Oxygen After Cardiac Arrest: Too Much of a Good Thing?
Patients who have excessive oxygen levels in arterial blood (hyperoxia) following resuscitation from cardiac arrest have a higher rate of death in the hospital compared to similar patients without arterial hyperoxia.
The most common lethal consequence of cardiovascular disease is sudden cardiac arrest. Even if return of spontaneous circulation (ROSC) from cardiac arrest is achieved, approximately 60 percent of patients will not survive to hospital discharge.
"In the search for modifiable post-ROSC factors, the role of supplemental oxygen, which is often administered in high concentrations to patients after cardiac arrest, has come into controversy," the authors were quoted as saying. "Laboratory investigations suggest that exposure to hyperoxia after resuscitation from cardiac arrest may worsen anoxic brain injury; however, clinical data are lacking."
J. Hope Kilgannon, M.D., of Cooper University Hospital in Camden, N.J., and colleagues conducted a study to determine whether hyperoxia after ROSC from cardiac arrest was associated with poor clinical outcome. The study included information from a critical care database of intensive care units (ICUs) at 120 U.S. hospitals between 2001 and 2005. Patients were older than 17 years, had non-traumatic cardiac arrest, cardiopulmonary resuscitation within 24 hours prior to ICU arrival, and arterial blood gas analysis performed within 24 hours following ICU arrival. Patients were divided into three groups based on a measurement of oxygen in arterial blood.
Of 6,326 patients, 18 percent had hyperoxia, 63 percent had hypoxia (deficiency of oxygen in the blood), and 19 percent had normoxia (normal level of oxygen in the blood).
Mortality was 63 percent in the hyperoxia group, compared with 57 percent in the hypoxia group and 45 percent in the normoxia group. "Exposure to hyperoxia was found to be a significant predictor of in-hospital death," the authors wrote.
The researchers also found that among hospital survivors, hyperoxia was associated with a lower likelihood of independent functional status at hospital discharge.
"While we acknowledge that association does not necessarily imply causation,” they wrote, “these data support the hypothesis that high oxygen delivery in the post-cardiac arrest setting may have adverse effects."
SOURCE: Journal of the American Medical Association (JAMA), June 2, 2010